Manufacture of reinforced hollow structures



July 24, 1951 s. MACERATA ,MANUFACTURE OF REINF ORCED HOLLOW STRUCTURESFiled July 18, 1947 .a w A R M @AO o .n U A m Patented July 24, `1951MANUFACTURE or REINFonoEnnoLLow STRUCTURES Stelio Macerata,Johannesburg, Transvaal,

' Union of South Africa I Application July 18, 1947, 'Serial No. 761,930In the Union of South Africa August 12, 1946 `1o claims. (on ca -154i'I'his invention relates to a method of manui l facturing hollowstructures, and to structures produced by such method. The invention isparticularly applicable to the manufacture oftanks,

silos, bins, towers (such as cooling towers), hop- K pers, chimneys,domes and the like.

The main object of this invention is to enable the application to suchstructures of the Hoyer method of reinforcement by means of prestressedwires.

A method according to this invention comprises the steps of so arranginga reinforcing wire that it has, in plan, the shape of an open or closedfigure having a plurality of straight sides (such as a polygon) thedirection of the wire being.

except at the free ends of such wire where the direction may or may notbe reversed, so reversed at each corner of the figure that the wire has,at each such corner, a loop projecting beyond that cross-section of theintended hollow structure at which such loop is located; tensioning saidwire by application of suitable tensioning means at its free end or endsand possibly also at one or more of said loops; casting or otherwisemoulding the structure so that the sides of the wire figure are partlyembedded therein and so that said loops or parts thereof project fromsaid structure; allowing the moulded material to .harden to the requiredextent; and then preferably cutting olf or otherwise removing saidprojecting wire loops.

Generally, the wire will have the shape of a spiral which is polygonalin plan and which may extend along the whole or part of the height ofthe structure that is to be erected and one or `more such spirals may beincorporated in each structure. In some cases it is preferable so toincorporate in some part of the structure two or more polygonal spiralsthat each side of each spiral crosses, at least in plan, at least oneside 4reinforced hollow structure.

of at least one other wire spiral. When two or more polygonal wirespirals are provided within the same length of the longitudinal sectionof the structure, the corresponding sides of the wire polygons arepreferably differently or oppositely inclined with respect to thelongitudinal axis of the structure and are thus also inclined withrespect to one another. In thismanner, it is possible to reinforce thestructure in two, preferably opposite, directions.

When the projecting loops are cut 01T, they leave all the sections ofthe wire or wires which remain within the shell of the structurepretensioned to the desired degree.

In a preferred form of carrying out the invention, the guiding means ateach, except one, corner of the wire figure comprises a fixed sheave ora pair of lxed sheaves, whilst at Said one corner there is provided atensioning means which vcomprises the combination of a xed sheave with amovable sheave, which is constrained for movement along a fixed rail andwith means, which may be operated by a hydraulic jack, for forcingsaidwmovable sheave in the direction away from said fixed sheave.

If'the hollow structure which is to be erected is polygonal in plan, atleast one reinforcing wire is preferably so arranged that all the loopsof that wire are formed at the corners of said structure and so thateach side of the polygonal structure has a length of the reinforcingwire extending throughout the whole length of such side.

If, on the other hand, the hollow structure is round, each reinforcingwire will be arranged, in plan, in the form of an eightor more-sidedpolygon so that a substantial part of the length of each side of suchpolygon will be `embedded in 'the shell of the structure when the latterhas been completed.

The invention will be further described with reference to theaccompanying drawings, in which:

Figure 1 is a plan section of a gonal structure.

Figure 2 is a part of a plan section of a round reinforced poly- Figure3 is a diagrammatic View of a polygonal structure the walls of which arereinforced in several directions.

With reference to Figure l, 2 and 3 indicate two .parallel reinforcingwires and 4 indicates the throughout the whole length of each of itssides.

' At the corner II, each wire is guided about a stationary sheave I2 andabout a movable sheave I3, which is constrained for movement along afixed' rail I4. I5 indicates a means, which may `be operated by ahydraulic jack, for forcing said movablejsheave I3 in the direction awayfrom said fixed sheave I2.

In carrying out the invention, rst a scaffolding I6 is erected to whichthe sheaves are secured in is required, or it may be formed by casting,pref-V erably with the use of vibrators, in which .case internal andexternal shuttering walls will be" erected from which the loops I1, ofpre-tensioned wire project at the corners. H

After the cementitious material has sufficiently solidied, theshuttering is removed andthe wire loops Il are cut off leaving thecompleted structure in which all sections of the reinforcing wire are`under tension, thus producing the required degree of compressive stressin the whole ,shell of the structure.

Instead of or in addition to the wires 2, 3, a reinforcing wire i8 maybe provided which is guided about fixed sheaves I9. The one end of saidwire IS may be fixed and the other end, 2 l, will be tensioned bysuitable means which are not shown in the figure.

i In the arrangement of Figure 2, the structure 22 which is to beerected is circular, and the two reinforcing rods or wires 23 are soarranged that they form, in plan, two polygonal figures the the wire sothat the sides of the wire figure are partly embedded therein and sothat at least parts of said loops project from said material; andallowing the cementitious material to harden until it forms the hollowstructure.

i. 2,y A method as claimed in claim 1, comprising the steps of removingsuch parts of the wire as project from the set cementitious structure.

v 3. A method as claimed in claim 1, in which the wire is bent to form aspiral which is polygonalin plan and which extends along the whole of'the height of the structure that is to be vtractati-V 4;. Al method asclaimed in claim 1, in which sides of which cross one another in theVsame Y manner as do the lines of a star of David. The direction of thewires is reversed at the stationary sheaves 24 so that portions 25 ofeach wire extend within the plan of the structure while wire loops Vatproject beyond the plan of said structure. The.

ends 26 'of the wires are fixed as by being anchored to the scaifolding,and the ends 2'1 are tensioned by suitable means. After the structure 22has been formed from cementitious material,

the wire loops 28 projecting from said structure.

are preferably cut off. A y A,

As shown in Figure 3, the reinforcing wires which, in plan, appear aspolygonal figures, are

preferably arranged in the form of spirals. In Figure 3, two groups 29,38 of wires are shown' which reinforce respectively the sides 3l, 32,33, 34, 35, 36 and the sides 3|, 31, 33, 34, 33 and 356 of thestructure.

Each group of wires forms, during the manufacture Vof the structure, ateach ofthe corners from which said wires are shown to extend, a seriesof loops which project beyond said corners, said loops being cut olfafter the completion of the structure leaving the wires 29, 30,pretensioned to the desired degree.

I claim:

1. A method of manufacturing hollow structures comprising the steps ofbending a reinforcing wire to the shape of a figure which, in plan, hasa plurality of `straight sides, the direction of the wire being soreversed at each cor.- ner of the ligure that the wire has, at each suchcorner, a loop projecting beyond that cross-section of the intendedhollow structuregat which Yso such loop is located whereby to provvideV`a sharp a,

intersection of the reinforcing wire at eahcorner; tensioning said wireby applicationv of suitable means; applying cementitious material to thewire is bent to form a spiral which is polygonal plan and which extendsalong part of the height of the structure that is to be erected.

A method as claimed in claim 1, in which a plurality of reinforcingwires is used.

6. A method as claimed in claim 1, in which at least two wires are usedeach .of which is bent to the shape of a polygonal spiral, each side. feach spiral crossing, at least in plan, at least one `side of at leastone other wire spiral.

'7'. A method as claimed in claim 1, in which at least two wires areused within the same length of the longitudinal section of thestructure, each wire being bent to the shape of a polygonal spiral; thecorresponding sides of the wire polygons being differently inclined withrespect to the longitudinal axis of the structure and thus being alsoinclined with respect to one another.

8. A method as claimed in claim l, for erecting polygonal structures inwhich at least one reinforcing wire is so arranged that all the loops ofthat wire are formed at the corners of said structure and so that eachside of the polygonal structure has a length of the reinforcing wireextending throughout the whole length of such side.

9. A method as claimed in claim 1, for erecting circular structures, inwhich at least one reinforcing wire is bent to a figure which, in plan,has the shape of a'polygon having at least six sides, av substantialpart of the length Aof each side o f such polygon being arranged withinthe plan, at the corresponding section, of the shell of the structurethat is to be erected.

' 10. A method of manufacturing hollow struc'- ytures comprising thesteps of erecting scaffolding, fixing to said scaffolding a series ofsheaves spirally arranged; placing a reinforcing wire so that thedirection of the latter is reversed to form a loop around some of saidsheaves; tensioning said wire; erecting shuttering so that parts of theprestressed wire are within an area determined by said shuttering whilesaid sheaves are outside said area; placing cementitious material withinsuch shuttering; allowing said material to harden; and removing saidscaffolding, said sheaves and said shuttering.

STELIO MACERATA.

REFERENCES CITED Y The following references are of' record inthe le ofthis patent:

UNrTED STATES PATENTS r*2,444,011 Billner Jan. 7,1947

1. A METHOD OF MANUFACTURING HOLLOW STRUCTURES COMPRISING THE STEPS OFBENDING A REINFORCING WIRE TO THE SHAPE OF A FIGURE WHICH, IN PLAN, HASA PLURALITY OF STRAIGHT SIDES, THE DIRECTION OF THE WIRE BEING SOREVERSED AT EACH CORNER OF THE FIGURE THAT THE WIRE HAS, AT EACH SUCHCORNER, A LOOP PROJECTING BEYOND THAT CROSS-SECTION OF THE INTENDEDHOLLOW STRUCTURE AT WHICH SUCH LOOP IS LOCATED WHEREBY TO PROVIDE ASHARP INTERSECTION OF THE REINFORCING WIRE AT EACH CORNER; TENSIONINGSID WIRE BY APPLICATION OF SUITABLE MEANS; APPLYING CEMENTITIOUSMATERIAL TC THE WIRE SO THAT THE SIDES OF THE WIRE FIGURE ARE PARTLYEMBEDDED THEREIN AND SO THAT AT LEAST PARTS OF SAID LOOPS PROJECT FROMSAID MATERIAL; AND ALLOWING THE CEMENTITIOUS MATERIAL TO HARDEN UNTIL ITFORMS THE HOLLOW STRUCTURE.